Reflector



March 25, 1930. 5 A, ESKI|LSON 1,751,984

REFLECTOR Filed Dec. 50, 1926 "l Y o /r @25W/ 3 @M M Patented Mar. 25,1930 UNITED STATES PATENT OFFICE SVEN AUGUST ESKILSON, OF STOCKHOLM,SWEDEN, ASSIGNOR TO AMERICAN GAB- ACGUMULATOR COMPANY, OF ELIZABETH, NEWJERSEY, A CORPORATION OF NEW JERSEY REFLECTOR Application led December30, 1928. Serial No. 157,964.

My invention relates to reflectors which, within a certainpre-determined angle of effectivity, reflect light which impingsthereupon back in the direction of incidence; that is, in the directionfrom which the rays come. Such reflectors are well adapted for. use insignalling, display and other purposes.

The general object of the invention-is to provide a reflector of simpleconstruction and of a character such that it may be manufactured atrelatively small cost. y

It also is an object of the invention to provide a reflector consistingof a mass of transparent material, such as glass, the opposing surfacesof which are of convex spherical shape, the centers of the respectivespherical surfaces being co-incident.

A further object of the invention is to provide a reflector unitconsisting of a solid mass of transparent material, such as glass, thefront and rear surfaces of which are of convex spherical shape and thecenters of which are co-incidental, but the radii of which may be ofdierent lengths, the rear surface of Isaid unit being provided withlight reflecting means.

A still further object of the invention is to provide a reflector unitconsisting of a mass of transparent material having front and rearconvex surfaces of spherical shape, which surfaces have a common center,the radius of curvature of the front surface upon which the rays oflight impingebeing less than the radius of curvature of the rearsurface, and a reflector provided upon the rear spherical surface, thereflecting surface of the said reflector being concave.

Another and further object of the invention is to provide a reflectorcomprising a plurality of reflecting. units integrally or otherwisesecured together in contiguous relation to each other, the opposingsurfaces of the said units being convexly spherical and the rear surfaceof each unit being provided with a covering having a concave sphericalreflecting surface.

Other objects and advantages of the invention will be pointed out inthedescription thereof which follows, or will be apparent from suchdescription. In order that the inf vention may be readily understood andits many practical advantages fully appreciated, reference may be had tothe accompanying drawing in which I have illustrated one form ofmechanical embodiment thereof. However, it will be understood that theinvention is susceptible of embodiment in other forms of constructionthan that shown, and that various changes inthe details of constructionmay be made within the scope of the claims without departing from theprinciple of the invention.

Fig. 1 is a View in central longitudinal section of a reflector unitwhich ma be either circular or polygonal in cross section and theopposing ends of which are of convex, spherical shape, the rear end ofsaid unit including a reflector element having a concave sphericalsurface, the said view also showing a number of rays proceeding fromdifferent directions and impinging upon the front surface of thereflector unit, passing therethrough znd being reflected from thereflecting surace;

Fig. 2 is a similar view having a number of incident rays of light inparallel relation to each other and to the axial line which impinge uponthe front surface of the reflector unit and after passing through thetransparent mass thereof impinge upon the reectin surface of thereflector and are returned through the said mass and emerge from thefront face thereof;

Fig. 3 is a view of similar character in which the reflector unit isshown in full line position and also is indicated by dash and dot linesin two other positions angularly related to each other and to the fullline position, the saidview being shown for the purpose of demonstratingthe maximum range of effectivity of a reflector embodying the invention;

Fig. 4 isa face or plan view of a reflector comprising a plurality ofreflectors united together, preferably integrally;

Fig. 5 is a sectional view taken on the line 5 5 of Fig. 4; and

Fig. 6 is a similar view taken on the line 6-6 df Fig. 4 at right anglesto the plane in which Fig. 5 is taken. c

In Figs. 1, 2 and 3 inclusive, I have illustrated a sin le reflectorunit which will be referredA to 1n order that the principle of o erationor action may be set forth and exained. Such a unit as is illustrated inthese gures is operative as a reflector and may be employed as such forpractical purposes, but because of its small size the light beam whlchwill bereflected thereby would be of such diminutive area as not tofulfill with complete satisfaction the necessities of Ia'practicalstructure for commercial purposes. A structure for commercial purposespreferably should include a pluralit of such units arranged inco-operative re ation to each other. It would be possible to constructand 'emiloy a single transparent mass or lens` bo y of a' size to givesatisfaction commercially, but such a structure would be impracticalfrom a commercial standpoint because` of its weight and because of thegreat expense lincident to the large mass of material em ployed-therein'and to its manufacture.

The structure which is illustrated in Figs. 4 to 6 inclusive, and whichconsists of a multiplicity of reflector units like those illusf trated1n Figs. 1 to 3 inclusive united in contiguous relation to each other,is commercial- :ly ractical, and, because of the cheapness wit which -itmay be manufactured and its eiiiciency in operation, has been found tobe very desirable.

.In Figs. 1 to 3 inclusive of the drawings, I have shown a reflectorunit comprising a lens consisting of a mass or body 1 of transparentmaterial, such as glass, which may be of any desired or preferred shapein cross section.

If a single unit should be employed for any purpose it preferably shouldbe vcircular in cross section on account of its greater range ofefl'ectivity, but when a plurality or multiplicity of such units arecombined or united into a single unitary structure the respective unitspreferably should be polygonal in shape in cross section, for instance,hexagonal, as illustrated in Fig. 4 of the drawings, in order that theymay be placed in close or contiguous relation with respect to eachother.

Each lens mass or body 1 is provided with o posing convex sphericalsurfaces 2 and 3, t e former being the front, incident surface, that is,the surface upon which the light rays to be reflected impinge. Theseopposing spherical surfaces, 2 and 3, have a common center 4.

The rear surface 3 is provided with a coating 5, the concave surface ofvwhich is light reflecting and is in effect coincidental with thesurface 3 although it may be spaced slightly therefrom. Preferably thiscoating should be formed by causing it to adhere by any suitable meansand in any suitable manner to the said surface 3. The said coating maybe applied in the same manner as reflecting coatings are applied toordinary mirrors.

The light rays impinge upon the front uncoated surface 2 ofthe lens bodyl of the reflector unit, and upon entering the said body are refractedand when they impinge upon the reflecting surface of the coating 5 uponthe rear surface 3 are returned by reflection through the lens body andare again refracted as they emerge from said body into the at mosphere.Such refraction takes place in both instances in accordance withWellvknown optical laws.

Because of the fact that the front or incident surface 2 of the lensbody 1 of the rey yare convergent to a point or focus a pre-determineddistance from said surface. This is independent of the angle ofincidence as is indicated in Fig. l.

In Fig. 1 I have indicated three iight rays, 6, 7 and 8 impinging uponthe surface 2 from different directions, that is, at different angles ofincidence. These rays are parallel respectively with the axial lines9,10 and l1 and are located at such distance therefrom that theyintersect the lines 9, 10 and 11 at the point Where those lines inipingeupon the reflecting surface of the reflector 5, in consequence of whichthe reflected rays indicated at 12, 13 and 14 after emerging from thelens body 1 into the atmosphere are parallel With the respectiveincident rays 6, 7 and 8.

The radii of the two spherical surfaces 2 and 3 are designated by thereference letters 3,.

r1 and r2 respectively.

In describing Fig. 1 I have chosen or referred to single rays, but inFig. 2 of the drawings I have indicated by means of a plurality ofparallel incident rays, 15, 16 and 17 which are parallel to the axialline 10, avvide beam of incident light. The day 15 impinges upon thesurface 2 at a point near its outer edge. It will be noted that it isrefracted so that it cuts the axial line 10 at a point 20, aconsiderable distance inside the reflecting surface.l Upon reference tothe parallel incident ray 16, it will be noted that after entering thebody 1 it is so refracted that it is caused to intersect the axial line10 at the point 21 upon the reliecting surface of the reflectors 5which, as already indicated, is substantially co-incident with thesurface 3.

Referring now to the incident ray 17, it will be seen that it isrefracted in a direction such that it cuts or intersects an extension ofthe axial line 10 at a point 22 beyond the surface 3. and beyond thereflecting surface of the reflector 5. The rays 15, 16 and 17, afterrefraction, iinpnge upon the reflecting surface ofthe reflector 5 andare returned through the body l and emerge therefrom in the directionsindicated by the lines 23, 24 and 25.

The first reflected ray designated by 23 is convergent with respect tothe axial line 10. The next reflected ray designated by the line 24 isparallel to the said axial line, while the next reflected ray, 25, isdivergent with respect to the said axial line. The angle between anincident or reflected ray and the axial line or a line arallel with saidline is known as the ang e of divergence and is indicated in Fig. 2 atc1 and c2.

rIhe reflector surface in a reflector unit of the character disclosedherein should be placed at such distance from the front surface of thelens body as to insure the reflec-` tion of the greatest possible amountof light at the lowest or least possible angle of divergence. Thedistance at which the result is accomplished is dependent on the indexof refraction of the transparent material emloyed in the construction ofthe lens body.

t is necessary that the reflecting surface be placed at such positionthat it intersects or cuts the axial line 10 at some point between thepoints 20 and 22, to which previous reference has been made.

It has been established by mathematical calculation and by design thatthe. best resulting reflection will be obtained when the relationbetween the radii r1 and r2 of the respective surfaces 2 and 3 (thelatter representing in effect the reflecting surface of the refletctor 5as well as the rear surface of the body l) is determined by thefollowing for- In this formula n represents the index of refraction ofthe transparent lens body. If it be assumed that the transparent lensbody l, preferably of glass, has an index of refraction of 1.53 it willbe found that the ratio of r1 torg is as4to 6.

Even if the incident light rays impinge upon the incident surface of thelens at angles to the axis of symmetry or axial line of the lensindicated by the line l0 in the drawings, the said light rays will bereflected at the .same angle of divergence as heretofore indicated;thatV is, the light rays in the reflected light beam will be distributedin the same manner irrespective of the angle of incidence of the beam.This. of course. has reference to the case in which the light beamstrikes the incident surface within the angle of effectivity indicatedin Fig. 3 of the drawings as the angle a. In said Fig. 3 it will benoted that the dash and dot lines 26 and 27 which are drawn through thepoint 4 which is the center of the two surfaces 2 and 3, cut the surface3' at points adjacent the side surface of the lcns body. It will be seenthat rays of light drawn through the center 4 and making with each othera greater angle than the angle a shown in Fig. 3, would not cut orintersect the rear surface 3 but on the contrary would cut or intersectthe side surface of the lens body and therefore would not be reflected.It is apparent therefore that the angle a constitutes the angle ofeffectvity of the unit.

The effectiveness of the unit for reflecting rays back and in thedirection whence they came within the angular limit stated is indicatedby the different indicated positions of the lens with respect to theincident rays as shown in Fig. 3 of the drawings. One position of theunit is shown in full line while the two other positions are indicatedby the dash and dot lines 28 and 29.

As already indicated these units may be united and combined into asingle unitary structure. Such a structure is shown in Figs. 4 to 6inclusive of the drawings, wherein it will be seen that a plate 30 oftransparent material is provided with a plurality or multiplicity of thesaid units united either integrally or otherwise so that they arecontigucusly related to each other as is clearl indicated in Fig. 4 ofthe drawings. l hen so related the spherical surfaces of all of theunits are hexagonal in shape except those at the outer edges of thegroup. The said plate consists of a plurality of such units so that thefront surface thereof comprises a plurality of convex spherical surfaces2 upon which the light rays from any source located in proper relationthereto impinge, While the rear surface thereof comprises a plurality ormultiplicity of convex spherical surfaces 3. The entire rear surface ofthe plate 30 is provided with coating material of which the portionsthereof upon the convex surfaces 3 cons'titute reflectors having concavereflecting surfaces. As already indicated with respect to the units,this coating may be applied or deposited in any suitable known manner.

The reflecting coating 5 upon the plate 30 may be protected by means ofa covering which may consist of a thin sheet or coating of copper 3l(applied electrolytically or otherwise) or by means of paint, pitch,cement or any other suitable substance which may be placed thereover.The coating 5 upon single reflecting units should likewise be protectedby means of a coating or sheet of copper or by other overlyingprotecting means.

The plate 30 is provided with a rim 32 which facilitates the mounting ofthe reflector shown in Figs. 4 to 6 in or upon a support therefor.

In the manufacture of a reflector such as is shown in Figs. 4 to 6inclusive the sheet 30 may be of a thickness to provide lens elements orunits in which the convex surface 2 will which the radius of the convexsurface 3 will have a radius of 6 mm.

In the use of reflectors embodying the invention single reiectorelements such as are shown in Figs. 1 to 3 inclusive may be arranged soas to form letters, signs and the like for giving signals, warnings,etc.\ If desired, coloring of. the reflected light may be effected byplacing over the reflectors a sheet of colored transparent material, thecolor being of the character desired.

It may be noted alsol .that letters or other symbols which may consistof opaque lines upon a transparent sheetor of translucent or transparentportions u n an opaque back-ground or of slots or openings in an opaquesheet may be rendered visible by placY ing the same over a reflectorcomprislng a plurality or multiplicity of reflecting units of thecharacter illustrated in Figs.` 4 to 6 of the drawings. A

It will be seen that by my inventionI have provided a structure in whichthe incident and reflecting surfaces are of a character such thatreflecting devices may be manufactured With a minimum of expense. For-instance, the glass sheet with the convex spherical .surfaces 2 and 3upon opposite sides thereof may be manufactured by pressing, rolling orlin any other manner which may be found to be practical.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. A light reflector structure comprising a sheet of transparentmaterial having the capacity of refracting light, the said sheet havinga plurality of contiguously related proj ecting spherical surfaces ofhexagonal shape upon its opposite sides, one of the said sides vconstituting the front surface 4of the sheet upon which the light raysimpinge and the other of said sides constituting the rear sur.- facefrom which the said rays are reflected, the said spherical surfacesbeing arranged in pairs in oppositely disposed relation to each other,the surfaces of the respective pairs having a common center, and meansfor rendering the rear spherical surfaces light refleeting, and saidsheet of transparent matethe rear side of said sheet of glass light re-l`of which rojects beyond the plane of the last name means.

3. A light reflector structure comprising a sheet of glass having uponits front side upon l- Which light' is adapted to impinge a plurality ofcontiguously related projecting spherical surfacesl of hexagonal shapeand also having upon its rear side a plurality of contiguously relatedprojecting spherical surfaces of like shape, each spherical surface uponthe front side of the said sheet of glass being opposed to a sphericalsurface upon the rear side thereof, the said two opposing surfaceshaving a common center, a coating upon the rear side of the said sheetof glass to render the said spherical surfaces light reflecting and aprotecting coating or sheet of metal or other suitable material mountedupon and overlying the first named coating to protect the same, and thesaid sheet of glass having a rim the rear edge of which projects beyondthe ing.

my invention, I have hereunto signed my name this 17 th day of December,1926.

SVEN AUGUST ESKILSON.

- rial having a rim, the rear edge of which v projects beyond a planetangent to the said rear spherical surfaces.

2. A light reflector structure consisting of a sheet of glass havingspherical projections upon its front side and spherical projections uponits rear side, the spherical surfaces ofA said projections beinghexagonal in shape, the said projections on both sides beingcontiguously related to each other and each spherica'l surface upon thefront side of said sheet of glass being opposed by a spherical surfaceupon the oplposite rear side thereof, the said opposed sp ericalsurfaces having the same center, means for rendering the surface upon Intestimony uthat I claim the foregoing as plane of the said protectingcoaty

